This invention relates to a spray treatment apparatus for small workpieces.
Such apparatus may take a variety of forms depending on the particular use to which it is to be put. For example, the apparatus may be provided in the form of a simple washing and rinsing apparatus having two or three stages or may be provided in a greatly extended form for the carrying out of surface treatment processes such as pickling of metal components.
To simplify the following description, the example of a spray washing and rinsing apparatus will be taken but it will be appreciated that, by suitably modifying the details of the apparatus, an apparatus of this type can be put to a large number of other uses.
It has been proposed, for example in British Patent Specification No. 1,035,852, to carry out a washing and rinsing process on small workpieces using a cylindrical drum having a horizontal axis, about which the drum is rotated in use. The drum is made of perforated material so that the treatment liquid can drain away and has an internal helical scroll or Archimedean screw feed means to feed the workpieces along the drum as it rotates. This arrangement has the disadvantage that the treatment liquid is only in contact with the workpieces for a very short time before it drains away through the perforations. Furthermore, any swarf or other small particles of material mixed in with the workpieces may tend to block the drainage holes in the drum so the treatment liquid builds up and has difficulty in draining away, which can result in one liquid being contaminated with that supplied at the next adjacent state for example.
One solution to this problem which has been proposed is on the lines described in British Patent Specification No. 1,558,566, in which imperforate drums are used and the Archimedean scroll is broken by small gaps so that liquid and swarf, but not workpieces, can pass through the scroll. The apparatus includes two or more barrels arranged coaxially about a rotational axis which is inclined to the horizontal. Treatment liquid is sprayed on the workpieces towards the upper end of each barrel and is then allowed to run back through the breaks in the Archimedean scroll to drainage means at the lower end of the barrel.
Unfortunately, this arrangement also has disadvantages when applied to any type of spray treatment machine of more than a couple of stages because each barrel has to be larger than the preceding barrel so that workpieces can feed directly from the upper end of a barrel into the lower end of the next succeeding barrel. Furthermore, the provision of an inclined axis means that, if the machine is extended in length, one end of the machine is likely to be very much higher than the other end, causing problems with factory space, loading and unloading.
It is with these problems in view that the present invention has been devised and it is an object of the invention to provide a spray treatment apparatus for small workpieces which overcomes or reduces these disadvantages.